Numerous animal and human studies have demonstrated an important hepatoprotective function of keratin intermediate filament (IF) proteins in several acute and chronic liver diseases. The hepatocyte IF cytoskeleton, which consists of keratin 8 and 18 (K8/K18) heterodimers, undergoes extensive physiological and disease- related reorganization that is mediated by post-translational modifications. Keratin-rich hepatocyte Mallory- Denk bodies (MDBs), and other histological alterations affecting the cytoskeleton, such as hepatocyte ballooning, are prominent features of alcoholic liver disease (ALD), nonalcoholic steatohepatitis (NASH), and other diseases characterized by oxidative injury and metabolic abnormalities. The objective of this application is to understand the regulation, functional significance, and liver disease relevance of keratin sumoylation. Sumoylation is a novel post-translational modification by Small Ubiquitin-like Modifier (SUMO) proteins with important implications to human disease pathogenesis. The central hypothesis of this proposal is that stress- induced keratin sumoylation participates in cross-talk with other post-translational modifications to regulate keratin properties and function during liver injury. Three specific aims will be pursued: (i) Characterize the regulatory mechanisms behind stress-induced K8/K18 sumoylation;(ii) Determine the functional significance of K8/K18 sumoylation;and (iii) Examine the regulation and significance of K8/K18 sumoylation in metabolic liver disease. The goals that the candidate will achieve through the proposed research and training plan include: learning novel techniques to study protein function and regulation;becoming adept at analysis of human and animal pathology;gaining expertise in cellular metabolic signaling and animal models of metabolic liver disease;and becoming grounded with the skills needed to become a successful independent investigator. The candidate's long-term career goals are to become an expert on intermediate filament proteins and their roles in human diseases, obtain a tenure-track faculty position and become a successful extramurally-funded independent investigator leading a strong research program in digestive disease related research. The research will be carried out at a premier institution (University of Michigan) and will involve primary mentorship from a leader in digestive disease related research;co-mentorship by two experts of metabolic signaling, diabetes, and insulin resistance;and collaborations with three experts of liver pathology, proteomics and post- translational protein regulation. The proposed research will provide mechanistic understanding of keratin regulation during metabolic and oxidative liver injury and may serve as the basis for novel approaches to treat common liver diseases, like ALD and NASH, where pharmacologic interventions are critically needed. Importantly, these studies will create new opportunities for investigation that the candidate will pursue during her independent research career stage. PUBLIC HEALTH RELEVANCE: There are over 80 human diseases that are caused or worsened by mutations in genes that encode various members of the intermediate filament family of proteins. This proposal specifically addresses the regulation and significance of keratin intermediate filaments in metabolically-induced liver disease. The results will provide insights into potential novel treatments for common liver diseases, such as those caused by obesity or alcohol consumption.